The present invention relates to printing presses, and pertains particularly to an improved ink system for lithographic printing presses.
The majority of lithographic printing presses have two ink form rollers of equal size for applying ink to the plate cylinder. A train of ink rollers transfers ink from an ink fountain to the two form rollers which apply the ink to the printing plates as the plate cylinder rotates.
Such lithographic presses are widely used and are satisfactory for most printing applications. However, where a printing job requires large areas of solid ink, heavy type, or high resolution half tones, the rollers develop ink deficient areas, often referred to as ink starvation.
This problem is solved to a large extent on larger printing presses by additional form rollers and ink trains that are built into the machines initially. Efforts to solve this problem for the smaller lithographic machines have been essentially unsuccessful. One problem with the lithographic presses is the lack of space to add additional form rollers and/or ink trains. The available space around the plate cylinder is taken up by the dampening system and the normally adequate existing ink system.
An example of a machine for which the above problems apply and for which the present invention is specifically designed to solve is the ATF-Davidson Company Chief models of machines as illustrated in FIG. 1 of the drawings and designed prior art. The construction and operation of these machines are more fully illustrated and described in the publication entitled Operator Manual for the ATF Chief Offset Duplicators; revised November, 1983 and published by ATF-Davidson Company, Whitinsville, Massachusetts, 01588. This publication is incorporated herein by reference.
This machine designated generally by the number 10, as schematically illustrated in FIG. 1, includes a frame comprising a pair of side frame members 12 and 14 between which the operating mechanism of the printing press is mounted. The press has a front end into which paper is fed at the right side of the illustrated embodiment and printing rollers to which the paper moves as it is being printed and discharged at the back or discharge end of the machine.
The roller arrangement for the inking and watering system of the machine is as illustrated in FIG. 1. The basis system includes a plate cylinder 16 with an ink train comprising a series of rollers extending outward in a substantially horizontal direction from the plate zone toward the rear of the machine. The inking system comprises a pair of form rollers 18 and 20 which are in rolling engagement with the plate cylinder and are engaged by a main oscillating roller 22, which oscillates along its axis as it transfers ink to the form rollers. A pair of idler rollers 24 and 26 are each respectively in rolling contact or engagement with the surfaces of the form rollers 18 and 20.
A back idler roller 28 is in rolling contact with the main oscillator 22 and with a distributor roller 30, which is intermittently contacted by a ductor roller 32, which oscillates transverse to its axis for transferring ink thereto from a fountain roller 34 which is in intermittently contact. An auxiliary oscillator roller is mounted above and in rolling contact with the back idler roller 28. The above described rollers have specific nomenclature and such nomenclature defines rollers of specific characteristics in the industry.
The dampening system for the printing press comprises a form roller 40 in rolling contact with the plate cylinder 16 and including an oscillator roller 42 in contact with the form roller 40. A ductor roller 44 oscillates transverse to its axis between a fountain or fountain roller 46 for transferring water from the fountain 46 to the oscillator roller 42. The ductor roller 44 is typically adjustable in its oscillation for adjusting the amount of moisture transferred from the fountain to the plate cylinder.
The above described arrangement is typical of the small printing presses of the lithographic type, and illustrates the problem encountered. The ink supply is typically insufficient for certain applications and as is typical, there is insufficient room typically to add another form roller or the like.
Therefore, it is desirable that an improved ink system for lithographic presses be available.